This section provides background information related to the present disclosure which is not necessarily prior art.
FIG. 1 is a view showing an example of a conventional III-nitride semiconductor light-emitting element. The III-nitride semiconductor light-emitting element includes a substrate 10, a buffer layer 20 grown on the substrate 10, an n-type III-nitride semiconductor layer 30 grown on the buffer layer 20, an active layer 40 grown on the n-type III-nitride semiconductor layer 30, a p-type III-nitride semiconductor layer 50 grown on the active layer 40, a current spreading electrode 60 formed on the p-type III-nitride semiconductor layer 50, a p-side pad electrode 70 formed on the current spreading electrode 60, an n-side electrode 80 formed on the n-type III-nitride semiconductor layer 30 exposed by mesa-etching the p-type III-nitride semiconductor layer 50 and the active layer 40, and a protective film 90.
With regard to the substrate 10, a GaN-based substrate may be used as a homo-substrate, and a sapphire substrate, a SiC substrate, a Si substrate or the like may be used as a hetero-substrate. However, any type of substrate may be employed as far as it can have a III-nitride semiconductor layer grown thereon. If the SiC substrate is used, the n-side electrode 80 can be formed on the SiC substrate-side.
FIG. 2 is a view showing an example of a conventional method of mounting the light-emitting element on a frame 5. The light-emitting element is secured to the frame 5 by means of an adhesive 9 such as Ag paste. Some of the light generated in the active layer 40 is directly emitted through the light-transmissive current spreading electrode 60, while light penetrating the substrate 10 is reflected on an Al layer 92 and emitted through the current spreading electrode 60 or the side surfaces of the light-emitting element.
The light-emitting element, which is a compound semiconductor light-emitting element, is very thin and is bonded to the adhesive 9 provided on the frame 5. Therefore, according to the conventional method of mounting the light-emitting element, as shown in a dotted-line circle 7 of FIG. 2, the adhesive 9 ascends to the side surfaces of the substrate 10. The adhesive 9, which may be opaque, absorbs some of the light introduced into the substrate. Even if the adhesive 9 is transparent, it still absorbs the light (though there is a difference in amount). As a result, the amount of light emitted from the light-emitting element decreases, which leads to low light extraction efficiency of the light-emitting element.